Refrigeration Cycle Control

September 9, 2015

Today the simplest form of controlling a refrigeration cycle is to use the temperature of the refrigerant and turn on or off the compressor based on the changes in refrigerant temperature. Many inexpensive and inefficient systems use a mechanical sealed bellows type that is filled with a gas, vapor or liquid, which responds to change in temperature by variation in volume causing expansion or contraction of a bellows that is connected to a micro switch. Based on the refrigerant temperature the switch will turn the compressor on or off.

This type of control is limited and it is very hard to achieve accuracy and precision in both the outcome (cooling) of the refrigeration cycle and the amount of energy used for operation of the system.

The next step up is to use a more accurate temperature sensor and provide control via a microprocessor. While this is an improvement, problems exist with this approach because one of the main items to be controlled is the compressor to control the pressure of the refrigerant. There are look-up tables for each refrigerant that show the relationship between temperature and pressure but they are not exact.

For the best control you ideally use a pressure transducer to measure the actual pressure of the refrigerant (high side and low side). Combine the actual pressure measurement with a microprocessor and you now can deliver precision cooling and tune the efficiency for best performance.

A reliable, repeatable and accurate pressure transducer will provide the best results and provide the best efficiency for your system. DunAn Sensing has designed the LP and HP series pressure transducers specifically for measuring low pressure and high pressure in any refrigeration cycle.

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